When Bom Kim dropped out of Harvard Business School to start a Korean e-commerce company in 2010, he found it difficult to attract workers. “‘Start-up’ did not have a good connotation in Korea,” he recalled.

Much has changed in four years. As the South Korean technology scene has developed, Mr. Kim’s start-up, Coupang, has flourished, growing rapidly and turning away thousands of job applicants.

Now Coupang has reached a new milestone: a valuation above $1 billion. The company is expected to announce later on Wednesday a $100 million round of financing led by Sequoia Capital, placing Coupang in an elite club of start-ups with 10-figure valuations.

The venture capital investors are betting that Coupang, which is based in Seoul and works with third-party merchants and also sells its own products, can continue to make inroads in the Korean retail business. The company, which competes locally with eBay and a site called 11th Street, says it differentiates itself by focusing on customer service and mobile shopping.

More than 70 percent of Coupang’s transactions are done on mobile devices, said Mr. Kim, the chief executive. And he said that most items purchased on the site can be delivered the same day or the next day. To ensure speedy service, the company even employs a staff of delivery workers.

“All of this makes us, we think, a glimpse into the future of e-commerce for the rest of the world,” Mr. Kim said.

Mr. Kim, who is 35, was born in Korea and moved to the United States as a child. He said he decided to start Coupang because a belief that the Korean market was a “hidden gem” that was “largely overlooked by investors and even more ignored by entrepreneurs.” In the company’s seed round of financing, the investors included the hedge fund manager William A. Ackman.

The company, whose items for sale range from beauty products to electronics to produce, would not disclose information about its revenue or profitability, but Mr. Kim said it recorded more than $1 billion of gross sales last year, a figure that measures the value of transactions on its platform.

Sequoia is investing in the company through two funds that are not as well-known as its venture capital business: Sequoia Capital Global Equities, which typically focuses on the public markets, and Sequoia Heritage, whose investments range from apartment buildings to hedge funds. The firm is using those funds because it does not have a venture capital fund dedicated to investments in Korea, a person briefed on the matter said.

Michael Moritz, the chairman of Sequoia, said in a statement that Coupang was “the leading online retailer in South Korea – one of the most attractive e-commerce markets in the world.”